Artificial arms



' M 7, 957 P; STEEPR- 2,790,976

ARTIFICIAL ARMS nid my 2;. 195a 'INVENTOR A TTORNEYJ ARTIFICIAL ARMS Charles P. Steeper, Roehampton, England Application July 2, 1953, Serial No. 365,717

5 Claims. (Cl. 3-125) This invention relates to an artifical arm assembly, which expression includes the arm proper and also the hand or other appliance. In the following description and claims hand will subsequently be used alone but it is to be read as including other appliances, which appliances are of numerous kinds, as is well known in the artifical limb industry.

The invention deals more especially with an artifical arm assembly of the kind having a hand which may be rotated relatively to the arm, or which may be removed from the arm. In this well known kind of artifical arm assembly it is the usual practice to have means for fixing the hand in any one of a number of positions or for releasing the hand for free rotation, or rotation to another position. Also in this kind of arm assembly a locking control is provided so that the hand is easily and quickly removable from the arm, whereby for example one appliance may be quickly substituted for another.

Previously arm assemblies of this kind have either had a wrist bisection or what is known as a midforearm bisection. For removability of the hand the wrist bisection is convenient because the locking control is easily asses sible, but in this case rotatability of the hand calls for a circular wrist, which does not conform to the natural oval wrist shape. To fit a hand rotatable at a wrist bisection with an oval wrist is not practicable, since the abutting oval faces of hand and arm would be out of register in most rotative positions of the hand relatively to the arm. On the other hand, for rotatability of the hand the mid-forearm bisection is better, since the nonbisected wrist can then be given the desired oval crosssection, that of the mid-forearm bisection being circular. However the disadvantage of this arrangement is that the locking control is not easily accessible when normal sleeved clothing is being worn. Thus an object of this invention is to provide an artifical arm assembly which has the desirable oval wrist shape and which also has the adjustably rotatable and removable hand, without the inconvenience of earlier constructions. Further the invention may provide an arm which is of neat appearance and is free of projections.

According to this invention an artifical arm assembly of the kind referred to is provided with a wrist bisection, for connection and removal of the hand, and a forearm bisection, such as at the mid-forearm position, for rotation of the hand and the lower portion of the forearm, the hand and forearm wrist-plates each having a like substantially oval periphery, and the forearm bisection being of circular periphery. Thus the hand wrist-plate and the forearm wrist-plate are each substantially oval in periphery so that when the wrist-plates abut on connecting the hand to the arm an oval wrist is formed. The forearm is divided into upper and lower portions connected together with their abutting ends each of circular periphery. The lower forearm portion is rotatable relatively to the upper portion, and thus the hand and lower portion may be I'O-l tated as desired, such as for retention in any one of several positions. Preferably an artificial arm assembly nited Sttes Patent 0 r 2,790,976 Ce Patented May 7, 1957 according to the invention has the manually operable controls, for permitting removal and fixing of the hand to the arm, and for rotatable adjustment of the hand, so arranged that they either do not project or project only slightly above the level of the adjacent surface of the arm, so as to give a neater appearance.

The preferred construction of arm assembly according to the invention will now be described in more detail, as an example, and with reference to the accompanying drawings, in which:

Figure 1 is a side elevation;

Figure 2 is a substantially horizontal, longitudinal section, with parts shown in top plan;

Figure 3 is a section on the plane III--III of Figure 2; and

Figure 4 is a section on the plane lV-IV of Figure 2.

Referring to the drawings, the forearm is divided or bisected at the mid-forearm position 1 into two separate portions, the upper and lower forearm portions 2 and 3 respectively. The upper end of the upper portion is connected by elbow mechanism to the upper arm 4. The lower end of the upper portion 2 is circular in crosssection and has a bearing referred to hereinafter for rotatably mounting the lower portion 3, whose upper end (see Figure 4) is also circular in cross-section and contains the mechanism for operating the release or locking of rotation of the lower portion 3 and hand 5. The lower forearm portion 3 is shaped so that whilst its upper end is circular its lower end and wrist-plate 6, to which the hand 5 is attachable, is oval in cross-section (see Figure 3), the wrist-plate 7 of the hand being correspondingly shaped.

The bearing between the upper and lower forearm per tions, at the bisection 1, is formed on the one hand by an inwardly directed flange 2A on the lower end of the upper portion 2 and on the other hand by the end 3A, the flange 2A and the end 3A abutting at the division 1 in a plane at right angles to the forearm axis. Abutti-ng against and overlapping the upper surface of the flange 2A is a circular plate 3C which is fixed centrally in any suitable manner to an extension 3B of the end 3A and thus holds the flange 2A in rotatable association with the end 3A. Five equally spaced holes, of which four are shown at 8A, are drilled in the flange, for selective engagement by a locking bolt 8 slidably mounted in a tube 9 fixed to a mounting plate 9A, which is itself fixed to the end 3A by screws 9B. The bolt movement is parallel to the forearm axis and the bolt 8 may be retracted against a spring it) in the tube 9 to permit free rotation of the lower forearm portion relatively to the upper portion, or it may engage, under the spring pressure, any one of the five holes 8A to lock the lower portion 3 in a desired position in relation to the upper portion 2.

As has been stated the bolt 8 is moved to the locking position by the spring 10. It is retracted by an external control member comprising a curved finger plate l1 (see Figures 1 and 2) projecting into an opening in the lower forearm portion 3, such that it protrudes only slightly oeyond the outer surface of the forearm. The finger plate 11 is mounted on a sliding plate 12 by means of a screw 11A (see Figure 4), the plate 12 being slida'oly mounted with respect to the mounting plate 9A. A tension coil spring 12A is fixed at one end by being connected to a pin 12B, fixed in the plate 9A, and is movable at the other end by being connected to a similar pin 12C, fixed in the sliding plate 12. The coil spring 12A tends always to move the sliding plate 12 to the outward position shown in Figures 2 and 4 and thus the finger plate 11 may be pushed inwardly against the spring 12A, which returns the member to the outward position when the manual pressure is released.

The sliding plate 12 is held slidably in position on the mounting plate 9A because its side edges are in slidable contact with the tube 9, the pin 12B, a pin 9C (mounted on the plate 9A), and one side of a bridge piece 9D, beneath which the plate 12 slides.

The plate 12 carries a pawl 13 pivotaliy mounted at 13A, which pawl is pressed by a light wire spring 14 into engagement with 'a ratchet wheel 15 rotatably mounted on the locking bolt tube 9. On its upper surface the ratchet wheel 15 carries a number of cam depressions 16 and 16A arranged to engage a pin 17 which is fixed to the bolt 8 and extends at right angles to it and runs in a slot 17A in the tube 9. When the control member 11 is pushed inwardly alternate movements rotate the ratchet wheel 15 so that the pin 17 rides into a depression 16 or a depression 16A, these depressions being alternately deep and shallow; a shallow depression 16A holds the bolt out of engagement with a hole in the upper portion 2; a deep depression 16 allows the bolt to engage a hole and lock the hand and lower forearm 3 against rotation.

The hand connection with the lower end 6 of the lower forearm portion 3 follows the usual construction and has a connector piece 18 extending axially from the hand for entry into a central socket 19 extending into the lower forearm portion 3 from its wristpl'ate 6. The connector piece has a rounded or frustoconical head 18A, below which an annular groove 18B is cut. When the piece 18 is inserted in the socket 19 the head 18A deflects a blade catch 20 (see Figure 3),.against the pressure of a spring 21, and when the piece 18 is pushed home the catch 20, under the influence of its spring 21, enters the groove 18B and prevents withdrawal of the hand, which is thus fixed to the arm.

This hand-connecting arrangement must be modified to prevent rotation of the hand and a transverse bar 19A is fitted across the socket 19 near its inner extremity. When the piece 18 is pushed home, the bar 19A engages in a slot 19B cut across the head 18A of the piece 18, and thus prevents rotation of the hand relatively to the lower forearm portion 3.

When the hand is to be removed, the catch 20 is retracted from the groove 18B and the piece 18 may then be withdrawn from the socket 19. The catch 20 is operated by an external finger piece 21A which is the same as the finger piece 11 described above, and is manually operable in the same way. It is preferably however rather smaller than the finger piece 11.

The catch 20 operates in the usual manner through a part-circumferential slot in the socket wall, the blade forming part of a half-annular rocker member 20A which is rockably mounted at 20B on the socket wall. One end of the rocker member 20A is engaged by the inner end of a plunger 22, slidable in a bearing 22A carried on the inside of the arm casing, the plunger 22 being fixed at its other end to the underside of the finger piece 21A. The other end of the rocker member 20A is connected to the tension spring 21, and the member is rockable onthe pivot 20B. Thus pressure on the finger-piece 21A moves it and the plunger 22 inwardly to rock the member 20A on its pivot 20B and so retract the catch 20. When pressure is released from the finger-piece the tension spring moves the catch inwardly and the finger-piece outwardly.

What I claim is:

1. An artificial arm assembly comprising an upper arm,

a forearm, said forearm having an upper part and a lower part, said upper part being connected to said upper arm and said lower part being rotatably connected to said upper part for axial rotation relatively thereto, a hand removably connected to said lower part, a latch in said lower part for retaining said hand, an external control member for operating said latch, saidlatch control member being movable on an axis normal to the axis of said forearm,

a bolt in said lower part, a plurality of spaced apertures in said upper part, a spring acting on said bolt to urge it towards said upper part, bolt operating means adapted to retract said bolt against said spring to inoperative position to permit rotation of said lower part and adapted also to permit said bolt to enter any one of said apertures depression of said external latch control member causing said latch to move against said spring for releasing said hand.

3. An artificial arm assembly according to claim 1 wherein said bolt-operating means comprises a tube, said bolt and said bolt-operating spring being housed within said tube, which is mounted within said lower part parallel to the axis of said lower part, a slot in said tube, a pin fixed to said bolt and projecting through said slot externally of said tube, a ratchet wheel freely rotatably mounted on said tube, a collar on said ratchet wheel and cam depressions on said collar, said pin being engageable with said depressions, such that alternate movements of said ratchet wheel retract said bolt from one of said apertures or permit said bolt to enter one of said apertures.

4. An artificial arm assembly according to claim 3 wherein said bolt control member is fixed on a plate, said plate being slidably mounted in said lower forearm part, a bolt being slidably mounted in said member, a spring being associated with said plate to cause said member to move outwardly to normal position, whence it may be manually inwardly depressed against said spring, and a pawl being mounted on said slidable plate, said pawl being held in engagement with said ratchet wheel for move ment of said wheel, said collar, said pin and said bolt control member each time said member is depressed.

5. An artificial arm assembly according to claim 1 wherein said upper forearm part has five 'of said spaced apertures, giving a plurality of positions of rotational adjustment of said lower part relative to said upper part.

References Cited in the file of this patent UNITED STATES PATENTS 767,201 Bennett Aug. 9, 1904 1,507,682 Pecorella et a1. Sept 9, 1924 FOREIGN PATENTS 559,216 Great Britain Feb. 9, 1944 616,942 Great Britain Jan. 28, 1949 

